It has been difficult to miniaturize the volume and the weight of conventional cathode ray tube (CRT) devices, and therefore liquid crystal display (LCD) devices characterized by compact size and excellent image qualities have gradually taken the place of CRT devices. Different from the CRT devices, the LCD device itself does not emit light. A back light source is required in an LCD device to emit lights.
Usually, the back light devices are generally classified into two types: an edge type and a direct type. The edge type back light device includes a lamp typically arranged on an edge side of the LCD device, a light guide plate disposed on a side surface of the lamp, a diffusion film disposed on top of the light guide plate, and a reflection plate disposed on bottom of the light guide plate. The light guide plate scatters rays irradiating from the lamp so that rays are uniformly incident into the diffusion film. The reflection plate reflects rays back to the diffusion plate so that most of the rays from the lamp are uniformly incident to the LCD panel by the diffusion plate.
Comparatively, the direct type back light device does not require a light guide plate. Linear light is directed to the display area from a light source via a diffusion plate and a reflection plate. Therefore, the direct type back light device is widely used in large sized LCD devices because it has high light transmission and does not have a limitation in the size of the display area.
In a conventional direct type back light device, each lamp is individually disposed on the frame or the reflection plate directly. These lamps are unable to be firmly positioned and secured, which results in leakage light or leakage currents, and more seriously, in damage of cables of power. Moreover, arranging the lamps directly on the frame complicates the disassembly procedure of the back light device when it needs repair. The replacement of individual lamp is generally performed in a clean room to reduce contaminations because of the complicated procedure. For example, when a lamp of the conventional back light device used in a LCD television needs to be replaced, the entire back light device has to be disassembled in a clean room, which makes on-site replacement impossible and delays the repair.
Therefore, there is a need to provide a back light module used in a back light device to simplify the assembly procedure and reduce the cost of assembly.